What you CAN do now is loan a book to someone else. Some publishers allow it, some don’t. Amazon takes it away from you for two weeks, then gives it back.
They’re also trying to work out the details on letting your local library loan you a book. Most of the other formats permit it now, and there are folks all over the country who have NY Public library cards for that purpose. With the difficulty in getting library funding these days, a method by which you could donate your Kindle book and the library could then loan it out to those who subscribe to their service could be a welcome source of revenue. As long as they limit the loan to one patron at a time, it seems like for a publisher it’d parallel what happens with a regular book.
Yes, that is new. I’ve never tried it. I think I got a notice from Amazon they have public libraries involved for lending.